The invention relates to magnetic recording media, and in particular, lapping of magnetic tape.
Magnetic tape is often used for storage and retrieval of data, and comes in many widths and lengths. Magnetic tape remains an economical medium for storing large amounts of data. For example, magnetic tape cartridges or spools of magnetic tape are often used to back up large amounts of data for large computing centers. Magnetic tape cartridges also find application in the backup of data stored on smaller computers such as workstations, desktop computers and laptop computers.
The creation of magnetic tape involves a number of different processing steps. For example, the processing may start with a wide roll of polymeric film, sometimes referred to as a stockroll. The wide film is then coated in a coating process. For example, the wide roll of film may be coated with a nonmagnetic underlayer followed by a magnetic layer on the front side and another layer on the back side to create a wide roll of magnetic tape. A calendaring process then is used to compress and smooth the coated magnetic material on the tape. The coating and calendaring processes typically require the tape to be un-spooled from a first stockroll and then re-spooled onto a second stockroll. After coating and calendaring, the wide roll of tape is typically cut in a slitting process to realize a number of narrow magnetically coated tape strands cut to the desired width. Again, this requires the roll of tape to be un-spooled. Each individually cut strand of magnetic tape typically is then re-spooled, and the individually spooled strands can be separated to realize individual xe2x80x9ctape pancakes.xe2x80x9d In this disclosure, a xe2x80x9ctape pancakexe2x80x9d refers to a spool of magnetic tape that has been cut to a desired width.
Each individual tape pancake is then typically un-spooled again and then burnished and wiped before being re-spooled. For example, the tape in each individual tape pancake may be burnished by scraping, vaming, lapping, or a combination of different burnishing techniques. Scraping techniques typically involve feeding the tape past a scraping mechanism to smooth or alter the surface of the tape. Vaming techniques utilize a rotating cylinder that rotates in a direction opposite the direction of incoming tape. The rotating cylinder, for example, is typically coated with industrial grade diamonds to smooth or alter the surface of the tape as it passes by and contacts the rotating cylinder. Lapping techniques are more complicated, but are generally more effective in burnishing the surface of the tape. Lapping techniques utilize a lapping film that is fed in a direction opposite the direction of incoming tape. For example, the lapping film may pass in one direction over a supporting structure referred to as a lapping shoe. The tape is passed over the lapping shoe in the opposite direction. The lapping shoe forces the lapping film into contact with the surface of the tape as the tape and lapping film feed past one another in opposite directions. In this manner, the lapping film can be used to effectively burnish the surface of the tape.
After burnishing, the tape is typically degaussed in a degaussing process. If desired, servo patterns can be magnetically written on the tape, and the tape may be spooled into a cartridge, which can then be sold as a magnetic tape cartridge. Alternatively, the burnished tape pancake may be sold with or without writing the servo patterns on the tape.
The various processing steps involved in producing magnetic tape are conventionally performed as separate and distinct stages. For example, the slitting process is typically performed independently from the other processes. Consequently, for each processing stage, the tape is typically un-spooled and processed, and then re-spooled. For this reason, each individual tape pancake typically requires handling by operators after slitting and prior to burnishing. This repeated handling can reduce media quality. In addition, the repeated spooling and un-spooling of the tape complicates the manufacturing process and can increase manufacturing costs.
In general, the invention is directed to techniques for inline lapping of magnetic tape. The lapping process is xe2x80x9cinlinexe2x80x9d in the sense that it is performed with one or more other magnetic tape manufacturing processes. In this manner, the invention is capable of reducing the number of times the magnetic tape is un-spooled and then re-spooled. Consequently, the amount of handling of the individual tape pancakes can also be reduced, thus avoiding damage to the edge of the tape, or other damage associated with tape pancake handling. Reducing the number of times the magnetic tape is spooled and un-spooled can also simplify the manufacturing process.
In various embodiments, the invention provides methods, apparatuses and systems for realizing inline lapping. Again, inline lapping refers to a lapping process that is integrated with one or more other tape processing steps. In other words, inline lapping does not require the tape to be un-spooled and then re-spooled solely for the lapping step of the magnetic tape manufacturing process. Rather, when the tape is un-spooled, both lapping and one or more other processing steps, such as the slitting process can be performed before the tape is re-spooled. Inline lapping can improve throughput, and at the same time may improve media quality.
In one embodiment, the invention integrates the tape slitting process and the lapping process into a single inline process. For example, a method may include un-spooling a roll of wide magnetic tape and cutting the wide magnetic tape into a number of individual narrow magnetic tape strands. The method may also include lapping each of the individual narrow magnetic tape strands prior to re-spooling, and then re-spooling each of the individual narrow magnetic tape strands. The tape may also be wiped or otherwise cleaned to remove debris prior to re-spooling. In particular, an inventive wipe unit as described in detail below can provide effective wiping of magnetic tape, especially at the tape edges.
For inline lapping to be more effective, the tension in each of the individual narrow magnetic tape strands can be separately controlled. For example, separately controlling tension in each of the individual narrow magnetic tape strands may involve controlling the torque with a number of magnetic clutch mechanisms, wherein each of the number of magnetic clutch mechanisms correspond to one of the individual narrow magnetic tape strands. Separate tension control for the individually cut narrow magnetic tape strands can help ensure that the lapping is more effective to smooth the magnetic surface of the tape and thereby reduce the likelihood of errors in the magnetic coating on the tape. In particular, tension control can make the result of the lapping process more uniform from strand to strand.
In one particular case, after cutting the wide magnetic tape into a number of individual narrow magnetic tape strands, the tape strands are separated into even numbered individual narrow magnetic tape strands and odd numbered individual narrow magnetic tape strands. In other words, individually cut narrow magnetic tape strands are separated such that every other strand is fed through one of two lapping units on an alternating basis. Thus, the even and odd numbered tape strands are formed adjacent one another in the slitting process, but separated for the lapping process.
In another embodiment, the invention is directed toward a lapping station for lapping magnetic tape. For example, the lapping station may include a first lapping unit that laps a first set of magnetic tape strands, and a second lapping unit that simultaneously laps a second set of magnetic tape strands. For example, even numbered individual narrow magnetic tape strands can be grouped in the first set and odd numbered individual narrow magnetic tape strands can be grouped in the second set. The first set of tape strands can be lapped by the first lapping unit, and the second set of tape strands can be lapped by the second lapping unit. The lapping units in the lapping station may adjustably engage the respective sets of magnetic tape strands. In this manner, the degree of lapping can be effectively controlled for each of the sets of tape strands on an independent basis. In some embodiments, a number of lapping units lap the first set of magnetic tape strands and a different number of lapping units simultaneously lap the second set of magnetic tape strands. For example, the different lapping units associated with each set of magnetic tape strands may lap different sides of the tape strands, or may utilize different lapping films to improve lapping on a given side of the tape strands.
The lapping station may further include wiping units or other cleaning units to wipe and clean the magnetic tape strands after the tape strands have been lapped. For example, the lapping station may include a first wiping unit that wipes the first set of magnetic tape strands, and a second wiping unit that simultaneously wipes the second set of magnetic tape strands. Each wiping unit may include a vacuum in fluid communication with a number of apertures to respectively draw the magnetic tape strands against a wiping material. The wiping material can move over the apertures in a direction opposite the magnetic tape strands. The vacuum can draw the tape strands into the apertures to improve wiping, especially at the edges of the tape strands.
In still another embodiment, the invention is directed toward an inline tape manufacturing system. For example, the system may include a slitting station that cuts a wide magnetic tape into a number of individual narrow magnetic tape strands, and a lapping station that simultaneously laps the number of individual narrow magnetic tape strands prior to re-spooling. The system may also include a re-spooling station that spools the number of individual narrow magnetic tape strands. Each re-spooled strand can then be removed to realize individual tape pancakes.
The slitting station can separate the number of individually cut narrow magnetic tape strands into even numbered individual narrow magnetic tape strands and odd numbered individual narrow magnetic tape strands. The lapping station may include one or more of the features described above, including lapping units and wiping units for lapping and wiping the individually cut narrow magnetic tape strands.
The rewind station may include tension control units to control tension in the individual narrow magnetic tape strands. In particular, the rewind station may include a first tension control unit to control tension in even numbered individual narrow magnetic tape strands and a second tension control unit to control tension in odd numbered individual narrow magnetic tape strands. For example, each of the first and second tension control units may include magnetic clutch mechanisms as described in greater detail below.
In still another embodiment, wide magnetic tape is passed through a lapping station that laps and possibly wipes the wide magnetic tape. The wide magnetic tape can then be sent through a slitting station to cut the wide magnetic tape into a number of individual narrow tape strands. The narrow strands may be lapped or wiped again, or otherwise cleaned prior to re-spooling.
The invention can provide a number of advantages. For example, inline lapping can improve burnishing compared to conventional burnishing techniques that utilize scraping or vaming. This, in turn, can directly improve media quality. In particular, inline lapping can smooth the surface of tape and reduce errors in the tape better than conventional vaming or scraping techniques.
Inline lapping can also improve throughput of the overall tape manufacturing process by allowing multiple individually cut narrow magnetic tape strands to be lapped simultaneously. This can save both time and capital resources. For example, conventional tape manufacturing systems may require a number of conventional lapping units to lap each individual tape pancake. The invention, in contrast, can replace the number of conventional lapping units with a single lapping station.
Moreover, because an intermediate step of un-spooling and then re-spooling the magnetic tape pancakes can be avoided in accordance with the invention, media quality can be improved. In particular, avoiding the intermediate un-spooling/re-spooling step can reduce the chance of airborne particles corrupting the tape. In addition, avoiding the intermediate un-spooling/re-spooling step can reduce the amount of handling of the tape pancakes by operators. Handling can cause damage to the tape, especially at the tape edges.
Additional advantages in terms of media quality can be achieved by incorporating wipe units in the inline lapping station. In particular, the wipe units described herein can provide improved media quality by removing debris from the tape. The wipe units described in greater detail below are particularly effective at removing dust and debris near the edges of the tape strands.
Inline lapping can also save time and energy by avoiding the need to clean rollers on conventional lapping units. For example, if a number of conventional lapping units are used, each lapping unit may require cleaning prior to lapping each individual tape pancake. The invention, however, can simultaneously lap a large number of individually cut magnetic tape strands using a lapping station. The time it takes to clean the lapping station may be significantly less than the time it takes to clean multiple conventional lapping units.
Still other advantages relate to the reduced complexity of the manufacturing process. The invention can reduce the number of stages involved in tape manufacturing by integrating the lapping stage with one or more other tape manufacturing stages, such as the tape slitting stage. This can reduce cost and complexity of the overall tape manufacturing process. In addition, inline lapping may reduce the amount of time it takes to manufacture magnetic tape.
Additional details of various embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.